Field of the Invention
The present invention relates to a novel process for preparing cis-alkoxy-substituted spirocyclic phenylacetylamino acid esters and cis-alkoxy-substituted spirocyclic 1H-pyrrolidine-2,4-dione derivatives, and also to novel intermediates and starting materials which are produced and/or used in the process according to the invention. Cis-alkoxy-substituted spirocyclic phenylacetylamino acid esters are important intermediates for the synthesis of insecticidal/acaricidal active compounds.
Description of Related Art
Cis-alkoxy-substituted spirocyclic phenylacetylamino acid esters are known, for example, from WO 04/007448. Cis-alkoxy-substituted spirocyclic phenylacetylamino acid esters of the formula (I) are obtained when cis-amino acid derivatives of the formula (VI)
are acylated with substituted phenylacetyl halides of the formula (VII)

(Chem. Reviews 52, 237-416 (1953); Bhattacharya, Indian J. Chem. 6, 341-5, 1968) or when cis-amino acids of the formula (VIII)
are acylated with substituted phenylacetyl halides of the formula (VII)
according to Schotten-Baumann (Organikum, VEB Deutscher Verlag der Wissenschaften, Berlin 1977, p. 505) and esterified (Chem. Ind. (London) 1568 (1968)).
In the current process, the cis-alkoxy-substituted spirocyclic phenylacetylamino acid (compounds of the formula (IIa)) is extracted with hot chlorobenzene. This solution is esterified with methanol under sulphuric acid catalysis to give compounds of the formula (I) (partial esterification of the compounds of the formula (IIa)). The non-esterified portion is recycled. Since the compounds of the formula (I) do not remain dissolved in chlorobenzene at room temperature, the solvent chlorobenzene is replaced by dimethylacetamide.
Particular disadvantages of this process are the unsatisfactory yield and the high expenditure for the process. Moreover, the solvents chlorobenzene and dimethylacetamide (DMAC) used are reluctantly employed. The disposal of the DMAC-containing waste water is associated with high costs.